FIGS. 1 and 2 illustrate a conventional fiber optic adaptor 2 having two opposite ends for respectively inserting male and female multi-fiber push-on (MPO) connectors 1, 3. The male MPO connector 1 has a coupling body 11 and a ferrule member 12 disposed on an end of the coupling body 11. The ferrule member 12 has a ferrule main body 121, two spaced-apart plug pins 122 extending through the ferrule main body 121, and a pin retainer 123 disposed at an end of the ferrule main body 121 for securing the plug pins 122 to the ferrule main body 121. The conventional fiber optic adaptor 2 has a housing 21 formed with an insertion hole 210, and two spaced-apart barb-shaped engagement members 22 mounted to an inner surface of the housing 21 within the insertion hole 210.
When the male MPO connector 1 is inserted into the insertion hole 210, the ferrule member 12 pushes the barb-shaped engagement members 22 to move away from each other. After the ferrule member 12 extends through the barb-shaped engagement members 22 into the insertion hole 210, the barb-shaped engagement members 22 return to their original positions and abuttingly engage the pin retainer 123 to prevent the ferrule member 12 from being detached from the conventional fiber optic adaptor 2. While only the barb-shaped engagement members 22 are used to limit movement of the pin retainer 123, because a front end of the ferrule main body 121 opposite to the pin retainer 123 is generally mated to the female fiber optic connector 3, no additional means is required to position further the male MPO connector 1. However, to remove the male MPO connector 1 from the conventional fiber optic adaptor 2, because the pin retainer 123 is hooked by the barb-shaped engagement members 22, directly pulling out the male MPO connector 1 requires large pulling force which can damage the male MPO connector 1 and the conventional fiber optic adaptor 2. In addition, because the barb-shaped engagement members 22 are disposed inside the insertion hole 210, a tool is needed to push the barb-shaped engagement members 22 away from each other, thereby increasing inconveniences for removal of the male MPO connector 1.